1. Field of the Invention
Internal combustion gasoline engine design is undergoing important changes to meet stricter emission standards set for engine and exhaust gas emissions. A significant change in engine design is the feeding of blow-by gases from the crankcase zone of the engine into the intake air-fuel mixture near the throttle plate of the carburetor rather than venting these gases to the atmosphere as was practiced formally. This blow-by gas contains substantial amounts of deposit-forming substances and it is known to form deposits in and around the throttle plate area of the carburetor. Another significant change in engine design and operation is the recirculation of a part of the exhaust gases to the fuel air intake of the engine. These exhaust gases also have a pronounced deposit-forming tendency. The carburetor deposits produced by the blow-by gases and the recycled exhaust gases restrict the flow of air through the carburetor at idle and at low speeds so that an over-rich fuel mixture results. This condition produces rough engine idling and/or stalling and leads to the release of excessive hydrocarbon emissions to the atmosphere.
Another problem associated with internal combustion engine operation relates to the crankcase lubricant and its use. Crankcase lubricating oils are inevitably contaminated with foreign substances such as dirt, water and decomposition products from the combustion process or from the breakdown of the lubricating oil itself. Significant amounts of sludge can be produced in the crankcase of an engine as a result of the presence of foreign matter and this sludge tends to adhere to the walls and passages in the engine. A particularly serious problem arises when the sludge in the crankcase lubricant deposits in the small passageways of the engine, thereby restricting the flow of the lubricating oil to bearings and valves in the engine. In the more serious instances, the oil flow through the oil passageways tends to be completely restricted resulting in a failure of the system to lubricate critical engine bearing surfaces. This condition leads to excessive cam shaft wear and ultimately to reduced engine life. An effective detergent in the crankcase lubricating oil serves to keep the foreign substances dispersed in the oil and also improves the effectiveness of the oil filter to remove a substantial amount of the foreign matter from the oil.
Another problem which always occurs where fuel and oil compositions are employed is the problem of corrosion. Engines and metal components in contact with a mineral oil and, more particularly, when they are employed in an environment that permits contact of the oil composition with water or water vapor tend to exhibit damage from corrosion. Additives which can impart effective corrosion-inhibiting properties to and oil composition while at the same imparting other useful characteristics such as detergent properties are particularly attractive additives for fuels and lubricants.
2. The Prior Art
U.S. Pat. No. 2,948,757 discloses a class of glycerol polyethers described as trihydroxypolyalkylene ethers of glycerol having anti-foam properties.